Recording means for busy telephone lines



Oct. 30, 1928.

S. V. C. SCRUBY ET AL RECORDING MEANS FOR BUSY TELEPHONE LINES Filed June 9, 1926 :v -m Jfb 3 L2 ===J mi* l;

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g l f N Patented Oct. 30, 1928.

UNITED STATES PATENT OFFICE.

SYDNEY VICTOR COLLARD SGRUBY, BASIL. ACKROYD TUBKHUD, AND FRANK DE FRE- MERY, OF ANTWERP, BELGIUM, ASSIGNES, BY MESNE ASSIGNMENTS, TO WEST- EBN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

RECORDING MEANS FOR BUSY TELEPHONE LINES.

Application led June 9, 1926, Serial No. 114,717, and in Great Britain July 9, 1925.

This invention relates to telephone eX- change systems and particularly to recording arrangements for such systems.

While it is customary 'for business houses as Well as other associations and individualsto subscribe for as many telephone lines as seem suflicient for their needs, it is often diiiicult to know Whether the number subscribed for is actually great enough since no record is made of the number of times a line is tested and found busy.

It is the object of the present invention to record the number of times a connection is attempted With a line While it is busy.

A feature of the invention is the provision of a recording device responsive to the reduced potential produced on the test terminal of a subscribers line by an attempted connection therewith While said line is busy.

A further feature of the invention is the use of a vacuum tube to render the above mentioned reduced potential effective to operate a recording device.

In the disclosed embodiment of the invention, the test terminal of a subscribers line is connected with the grid of a vacuum tube forming a part of the recording device. When the line is idle or busy With a call, the potential of the grid is suliicient to prevent current flow in the vacuum tube but when a second call is attempted the potential is reduced to such a point that current WillfloW in the tube. This current is assisted by a condenser discharge to cut oi the current flow in a second vacuum tube releasing a relay and operating a meter.

The drawing shows a subscribers line appearing in multiple terminals of a line finder and a plurality of final selectors. A portion of the connecting apparatus in each case is indicated diagrammatically. The apparatus Within the broken rectangle comprises the recording device which may be connected With any subscribers line.

The recording device 100 consists essentially of a meter 108 together With the controlling circuits therefor. These controlling circuits comprise a pair of vacuum tubes 101 and 102 and a relay 103 shunted by condenser 104. Battery 105 is used for supplying the filaments of the vacuum tubes and is lower in potential and opposite in polarity to batteries 106 and 107 which supply potential to the plates oi the vacuum tubes. No attempt has been made to indicate the relative potentials of the batteries. The subscribers line 1 is shown together with the multiple terminals in which it appears in the inal selec` tors 2 and 3 and line finder 4.

As indicated above, this circuit makes use of the change in potential of the subscribers test terminal. The potential of this terminal may have at different times any one of four values which occur under the following circumstances A-subscribei"s line free.

B-subscribers line busy.

C-busy subscribers line tested.

D-metering of' completed call.

When a subscribers line `is free, the sleeve terminal 6 Will have the full potential of the battery since no current is iiowing. When the subscriber-s line is in use, say with iinal selector 2, relay 5 Will be operated and a circuit Will be completed through that relay 5 to ground. In consequence, the potential of the sleeve terminal 6 Will be reduced. A similar condition arises when substation 1 is busy as a calling line. Ground is connected to the line finder terminal 13 through a resistance, not shown, as soon as the line has been associated With a selector. It a second linal selector, such as selector 3, tests the line While it is busy, ground Will also be connected to tei'- minal 6 through relay 7 and resistances 8 and 9. This Will further reduce the potential of terminal 6. rlhe fourth condition enumerated above occurs when the line has been busy asa calling line. It the outgoing call has been completed, apparatus (not shown) Will be actuated to connect battery 10 to the terminal 6 through the line finder for the purpose of operating meter 11. It Will be noted that battery 10 is oppositely polarized to the operating battery of cut-off relay 12. It is also of greater potential in order to overcome that connected to the message register. For a description of the operations which give rise to these conditions, reference may be made to U. S. Patent 1,365,269, granted to L. Polinkowslry, January 11, 1921.

When it is desired to test Whether a line or group of lines are sufficient, the recording device 100 is connected With the test terminal 6 of the subscribers line or the last line ot the group in any desirable manner. The filament battery switch 109 is closed and the filament current adjusted by means of ammeter 110 and adjustable resistance 111. Jack 112 is arranged to permit the inclusion or omission of ammeter 110 as desired. Jacks 114L and 115 also permit the checking of the plate voltage or the space current it' desired. The readings of service meter 11 and meter 108 are noted at the beginning of the period during which the line is to be under observation vWith the subscribers line free, full battery potential will be present on grid 113. This potential being muc-h more negative than thatotl the filament battery 105, no current will be permitted to flow between filament 116 and plate 117. Grid 120 of the second vacuum tube 101 is connected to the positive side of iilament 118 and will, therefore, be less negative than the iilament so that current will fiow between iilament 113 and plate 119. Relay 103 which is included in this circuit is operated, opening the circuit of meter 108. This steady condition continues as long as the line 1 is free.

Then a connection is established with the subscribers line 1, either as a calling line or as a called line, ground through a resistance is connected to the test terminal oi? the line, and, due to the current drain through said resistance, the potential ot terminal 6 is reduced. The grid 113, therefore, becomes less negative with respect to the iilament but the characteristics of the tube 102 are such that the steady condition, as above described, still persists and relay 1034 remains operated.

IVhennow al second Iinal switch, such as final selector 3, attempts a connection to subscribers line 1, ground through relay 7 and resistances 8 and 9 is connected to the test terminal of the line multipled before switch 3. This further reduces the negative potential of terminal 6, and in consequence, of grid 113. This reduction is sufficient to permit current to How between filament 116 and plate 117. The condenser 121 which is connected with plate 117 now discharges through resistance 122, increasing the negative potential of grid 120 to such a point that the current flow between filament 118 and plate 119 is substantially cut off. Relay 103 is, therefore, deenergized and closes the circuit of' meter 108 causing that meter to operate. As soon as the discharge from` condenser 121 ceases, a second steady conditionv is established, relay 103 is reoperated and meter 108 deenergized. Since the line is busy, relay 7 will not be operated and after a short interval the final selector will be disconnected from the terminals of line 1. As soon as the circuit of test relay 7 is open, grid 113 again becomes more negative than filament 116 and current ceases to flow through tube 1.02` Condenser 121 now charges slowly through resistance 123. The charging current through resistance 122 further reduces the negative potential of grid 120, thus strengthening the plate current through `relay 103 and holding that relay operated. When the condenser becomes fully charged, the first steady condition is again established.

On the release of a completed outgoingcall, a positive battery 10 is connected to the multiple terminal 13 in the line finder, operating service meter 11. This positive bat tery will make the terminal 6, and consequently grid 113, positive also. The condenser 121 will be discharged as above described and meter 108 will be operated.

It is apparent, from the foregoing description, that meter 108 will record all those completed connections recorded by service meter 11 as well as attempted connections to the line when the line is busy. From these records the number of ineffective calls, due to the line being busy, may be obtained.

Although the invention has been disclosed and described in connection with an automatic telephone system, it is clearly well applicable to manual systems. In such a manual system it would only be necessary to arrange that the recording apparatus respond to the usual manual busy test which occurs when the operator tests the sleeve off the line jack with the tipv of her calling plug. Since the meter and cut-off relay of a manual line are very etten connected to ground, a suggested arrangement would be the insertion of a high resistance sensitive relay in the con ductor 124 which would be operated upon the establishment of a connection to extend conductor 124 to4 grid 113.A Itis also. clear that other methods of coupling between the vacuum tubes could be used.

What is claimed is:

1. In a telephone system, lines, a recording device associated with one of said lines, means for interconnecting said line with a secondi line, meanswhereby an attempt may be made to connect a third line with said first line, and. vacuumA tube controlled means for recording said attempted connection.

2. In a telephone system., 1ines, a test terminal.- individual to one ot said lines, means for interconnecting said line with a second line, means whereby an attempt may be made to connect a third line with said first line, means for supplying characteristic potentials to said test terminal when.` said first line is free, when busy, and whenY a second: con.- nection is attempted, a recording device7 means for associating said device with said test terminal, and means responsive to the potential applied tosaid test terminal when a second connection is attempted to record said attempted connection.

In a telephone system, lines, a test terminal associatedwithone of. said lines, means for interconnecting said line with a second line, means-whereby an, attempt may be made to connect a third line with said' interconnected first line, means for applying successively reduced potentials to said test termina] when said first line is free, when busy, and When a second connection is attempted, a recording device, means for associating said device with said test terminal, and means in said recording device responsive to the reduced potential applied to said test terminal by said attempted connection to cause the re cording of said attempted connection.

4. In a telephone system, lines, a recording' device associated with one of said lines, means for interconnecting said line with a second line, means whereby an attempt may be made to connect a third line with said interconnected first line, a meter in said recording device, and means responsive to said attempted connection to create a momentary condenser' discharge current whereby said meter is operated once only.

5. In a telephone system, lines, a test terminal associated with one of said lines, means for interconnecting said line with a second line, means whereby an attempt may be made to connect a third line with said interconnected first line, means for applying potential to said test terminal when said first line is free, means for reducing' said potential when said first line is interconnected with another line, means for further reducing said potential when said second connection is attempted, a recording device, means for associating said device with said test terminal, a meter in said recording device, means in said recording device responsive to said :turther Kreduction of potential to produce a momentary current and means responsive to said momentary current to operate said meter.

6. In a telephone system, lines, a test ter minal associated with One of saidlines, means for interconnecting said line with a second line, means whereby an attempt may be made to connect a third line with said interconnected first line, means for applying potential to said test terminal when said first line is free, means for reducing said potential when such line is interconnected with another line, means for further reducing said potential when said second connection is attempted, a 'recording device including a vacuum tube, means for applying said potentials to the grid of said vacuum tube, a meter in said recording device, means associated with said vacuum tube whereby said further reduction of potential produces a momentary current and means responsive to said momentary current to operate said meter.

In witness whereof, we hereunto subscribe our names this third day of May A. D. 1926.

S. V. C. SCRUBY. B. A. TURKHUD. F. DE FREMERY. 

